Cathode-ray tubes for use in television receivers



cATHoDE-RAY TUBES EGR USE IN TELEVISION RECEIVERS Filed Oct. 29, 1954 E. WINTER July 2, 1957 5 Sheets-Sheet l INVENTOR. E RN O W I N TER BY m ,Dla/nv ATIORNEXS July 2, 1957 E. WINTER 2,798,180

CATHODE-RAY TUBES FOR USE IN TELEVISION RECEIVERS Filed Oct. 29, 1954 `15 Sheets-Sheet 2 Eg z - INVENTOR. ERNOv WNTER BY mudar/6M ATTORNEYS E. WINTER July 2, 1957 CATHODE-RAY TUBES FOR USE IN TELEVISION RECEIVERS 5 Sheets-Sheet 3 Filed Oct. 29, 1954 94W 7 4 d t v1.1. r, Mx..

INVENToR. ERNO W\ NTER BY fum-,@fm

ATTORNEYS United States Patent C i CATHODE-RAY TUBES FR USE IN TELEVISIN RECEIVERS Ern Winter, Budapest, Hungary, assigner to Egyesiiit Izzlmpa s Villamossgi Rszvnytrsasg, Budapest, Hungary, a Hungarian enterprise Application October 29, 1954, Serial No. 465,489

Claims priority, application Hungary November 5, 1953 Claims. (Cl. 313-82) This invention relates to cathode-ray tubes for use in television receivers. It is known that in tubes of this kind which are provided with a luminescent screen, negative ions are emitted together with electrons and said negative ions while bombarding energetically said screen cause the so-called ion-burn on the image screen of the tube. This ion burn forming a dark spot is generally worst in the centre of the screen.

ln order to prevent the occurrence of said ion burn on the luminescent screen of cathode-ray tubes for use in the reception of television, means have been provided by which negative ions are separated from the electron beam and intercepted by an ion trap electrode. The separation of the ion beam from the electron beam is effected by the action of a magnetic held generated by means of deflecting coils arranged outside the tube. These devices built inside and outside the tube are rather complicated and thus increase the production costs and weight of the device. It has also been proposed to deposit a very thin layer of metallic aluminum over the inside surface of the luminescent screen in order to prevent said ion burn. The deposition of a thin aluminum layer upon the screen of cathode-ray tubes is a Very complicated and expensive process and is not suitable for mass production.

it is one of the objects of this invention to eliminate the occurrence of negative ions in cathode-ray tubes as far as possible and thus to prevent the occurrence of said ion burn.

It is another object of this invention to facilitate the manufacture of cathode-ray tubes free from ion burn and to decrease production costs of said tubes especially that of television tubes.

A further object of this invention is a cathode-ray tube for television receivers with a new kind of cathode preventing substantially the emission of negative ions without providing any special and expensive devices. n

A still further object of this invention is a cathode for cathode-ray tubes which are practically free from ion spots.

Other objects and advantages will become apparent as the invention is more fully disclosed.

in our co-pending patent' application Ser. No. 429,954 there has been proposedVV a so-called supply cathode comprising a container body, a sintered porous body forming a closing member` for said container body made of a refractory metal having a melting point higher than that of nickel, said container body and said porous body enclosing a supply chamber, the pores ofsaid porous body forming the only passages fromy within said chamber onto the outer surface of said porous' sintered0 body. Within the said chamber there is accommodated a substance adapted to work as an active material of said cathode,l said substance comprising preferably more than one earth alkaline compound other than a carbonate, azide, boride, nitrate and having,y at least in activated condition`y of the cathode, a barium oxide content, the

Patented July 2, i957 ICC barium oxide tension of said substance being less than the tension of mere barium oxide.

In our co-pending patent application Ser. No. 429,955 there has been proposed a so-called supply cathode having a working surface and comprising a container body, a sintered porous body forming a closing member for said container body, said container body and said porous body enclosing a supply chamber the pores of said porous body forming the only passages from within said chamber onto the outer surface of said sintered body. Within the said chamber there is accommodated a substance containing at least one of the alkaline metals and alkaline earth metals adapted to yield, at least in the activated condition of the cathode, such a material in its metallic state through the passages in said porous body for continuously rendering said working surface active, whereby the porous body is formed by a metallic material having a content of at least one of the platinum metals, as described in our co-pending application Ser. No. 429,954, and is adapted to form an alloy with at least a substantial portion of the metal yielded by said supply substance along their contacting surfaces. Thus, the activating substance of this cathode consists of a compound and/ or an alloy containing at least one alkaline or earth alkaline metal.

According to this invention a cathode-ray tube comprises an electron gun containing a heated cathode, focusing means, deflecting means and a fluorescent screen, said cathode having a working surface and comprising a container body, a sintered porous body forming a closing member for said container body, said container body and said porous body enclosing a supply chamber, the pores of said porous body forming the only passages from within said chamber onto the outer surface of said porous sintered body, a supply substance provided within said supply chamber and adapted to work as the active material for said cathode, said porous body being formed by a metallic material having a content of at least one of the platinum metals and adapted to form an alloy with at least a substantial portion of the metal yielded by said supply substance along their contacting surfaces, said supply substance containing at least one of the alkaline and alkaline earth metals in form of an alloy and adapted to yield, at least in the activated state of the cathode, such a metal in its metallic state through the passages in said porous body for continuously rendering active said working surface.

It has been found that thevelocity of vaporization of said alloy is determined by theratio of the active and the inactive components contained in said alloy. Such a cathode according to the invention is particularly adapted for use in television receiver tubes, as the electron beam produced by the cathode is practically free from negative ions and causes no ion spot on the screen.

It has been found that for the purpose mentioned above cathodes are especially suitable comprising a sintered porous body of tungsten and/or molybdenum and/or tantalum and/or niobium and/or hafnium or made of an alloy of' two or more of these metals and further containing tone or more metals of the platinum group and/or which are coated with at least one metal of the platinum group, whereby the activator is a barium alloy, e. g. an alloy :of barium and of one or more metals of the group III of the periodic system. Good results have been obtained with an activator consisting of.50% barium and 50% aluminum. The speed of vaporization may be determined by the percentage of the components, i. e. by the ratio of the active and inactive components forming the activator. The composition of the activator determines also the working temperature. According to our experiments suicient quantities of barium reached at a temperature under 1000 C. in the case of using a barium alloy containing 50% barium and 50% aluminum. Barium forms a temporary alloy with the metals of the platinum group upon the active surface of the porous body. Thereby the tension of the metallic barium is lowered and thus the life-time of the cathode lengthened. In other cases good results have been obtained with activators consisting of 20% barium and 80% aluminum. The barium contents of the alloy may be as low as though preferably it will be more than The characteristic features of the invention are set forth in the appended claims and a preferred embodiment thereof is disclosed in the following specification and in the accompanying drawing in which Fig. 1 shows a cathode ray tube for use in television receivers in accordance with the invention and Fig. 2 shows a cathode constructed for the television tube according to Fig. 1 and attached to the inner mantle surface of a Wehneltcylinder. Fig. 3 illustrates partly in section a perspective view of a porous body made in compliance with the present invention. It is to be pointed out thatfor sake of clarity-the gures are not drawn to scale neither as regards their whole nor the interrelation of the parts illustrated.

The invention is applicable to any type of television tubes, but for purpose of illustration a conventional television tube is shown in the drawing with an envelope 1 enclosing an electron gun structure in the neck portion 2 of the envelope with the usual electrodes and a fluorescent screen 3 in the bulbulare portion of the envelope. The fluorescent layer consists e. g. of zinc sulphide. The electron gun contains a heated cathode or source of free electrons 4. The electrons leaving the electron gun pass through the hole of the electrode 5 which by being placed at higher or lower negative potentials can control the number of electrons passing. The electrons are accelerated by a positive potential 'on the focusing anode 6. This diaphragm serves to stop all electrons except those making a small angle with the axis of the beam.

The beam of electrons thus formed is further accelerated by the potential on the accelerating anode 7 with a hole 8 in its centre and is focused on the screen 3 at the end of the tube by the electron lens set up between the rst and second anodes 6 and 7.

' The number of electrons, and therefore the brightness of the spot, may be controlled by the potential on electrode 5; the focus or sharpness of the spot may be controlled by proper shaping of the electron lens by adjustment of the anode potentials.

Two pairs of deflection plates 9 and 10 are provided along the path of the electrons as usual on both sides of a diaphragm 11 provided with a slot 12.

The cathode 4 of the tube is shown with more details in Fig. 2 which isV a perspective view and partly an axial section. The cathode comprises a container body 16 made of molybdenum, nickel, tungsten or the like and a sintered porous body 17 hereinafter described in closer details, for serving as a closing means of the container b'ody 16 and forming with the latter a supply chamber 18. Within said chamber 18 there is provided a supply substance 19 selected so as to work as the active ma terial of the cathode and the composition of which will hereinafter be more particularly described. With the represented embodiment the supply substance 19 lls up the chamber 18 completely. However, it is possible to have it occupy but a portion of the chamber 18 as is known to those skilled in the art. Moreover, the container body 16 lits into a cylindrically shapedfvessel 20 made likewisely of molybdenum, nickel, tungsten or the like, leaving a disk like interstice or heating chamber 21 between the bottom of the container body 16 and a disklike insert 22 made of a ceramic material and snugly 4 fitted in the bottom part of the vessel 20. The mutual position of the container body 16, the closing part 17 and the supply substance 19 is determined by a shoulder `23 and by a rim 24 of the container body 16, respectively.

The mutual position of the container body 16 and the vessel 18 is likewisely secured by a shoulder 25 and a rim 26, respectively, of the vessel 20. Instead of by means of the shoulders 23 and 25 the mutual position of the said elements might as well be secured by any suitable means, e. g. by welding. Within the interstice or heating chamber 21 there is provided a heating means 27 for the cathode the supply leads of which are designated by reference numerals 28 and 29, respectively, and led through suitably formed registering guiding passages of the ceramic disk 22 and the bottom part of the vessel 20. In order to ensure an evenly distributed heating effect along the bottom surface of the body 16, the heating means 27 is formed as a flat spiral, the turns of which lie in a plane parallel to the bottom surface of the container body 16. The ceramic disk 22 might be substituted by a disk :of another suitable heat insulating material or dispensed with altogether.

The cathode as a whole is secured by annular fastening means 30 and 31, respectively, made of nickel, molybdenum or the like, to a disk 32 made of ceramic material, which, in turn, is secured by means of ring-shaped fastening means 33 and 34, respectively, made likewisely of nickel, molybdenum or the like, to the inner mantle surface of a Wehnelt-cylinder 35 well known in the art. The Wehnelt-cylinder 35 is composed of two symmetrical parts each of which is provided with brackets 36 and 37, respectively, forming together with their counterparts 36 and 37 loops 38 and 39 which are slidably arranged on rods 40 and 41 of ceramic material as is known in the art.

The supply substance 19 contains according to this invention at least one of the alkaline metals and/or the alkaline earth metals in the form of an alloy the components being selected so as to yield, at least in the activated condition of the cathode, such a metal in its metallic state as has been set forth in the preamble of this specification.

As to the closing member 17 formed by a sintered porous body, a portion thereof is illustrated on a larger scale in Fig. 3. As the result of the sintering process the grains of the material'forming the closing member 17 adhere to one another so as to confine the pores 42 therebetween which obviously form the only passages from within the supply chamber 18 onto the outer surface of the closing member 17. According to the invention the porous body is formed at least partly by a metallic material having a content of at least one of the platinum metals.

If the components for the closing member 17 and the supply substance 19 are selected in compliance with the present invention, the alkaline metal or the alkaline earth metal yielded in its metallic state by the supply substance 19 through the passages 42 in the porous body forming the closing member forms an alloy with the platinum metals of the closing member along their contacting surfaces thereby continuously rendering active the working surface 43 of the cathode.

As stated above the porous body canwithin the scope of the invention-'contain various compositions. The barium may be wholly or partly substituted by or mixed with any other alkaline metal or earth alkaline metal. Especially good results have been obtained by an alloy containing about 40% barium, about 10% calcium and about 50% aluminum. But aluminum may be mixed with or substituted by another suitable metal. Such metals are those of the group III of the Periodic System, for instance rare earth metals as scandium or yttrium,

Examples for alloys especially adapted for the porous body according to the invention, in addition to that mentioned above, are:

1. 48% Ba, 10% Sr, 50% Al 18% Ba, 82% Be Ba, 20% Al, 40% Ni 50% Ba, 10% Al, 40% Ni 40% Ba, 20% Be, 40% Ni 50% Ba, 42% Al, 8% La Lanthanum may be substituted by Scandium or Yttrium in quantities of about 8-12%.

Television tubes provided with a cathode according to this invention are practically free from ion spots, although no special devices such as ion traps have been applied inside the tube. The cathode according to the invention has further advantages, especially the long lifetime of the tube, as a result of the new cathode being a so-called supply cathode.

What I claim is:

l. A cathode-ray tube for use in television receivers, having an electron gun, accelerating electrodes, deecting means and a fluorescent screen, the cathode of the electron gun being a supply cathode having a working surface and comprising a container body, a sintered porous body for serving as `a closing member of said container body, said container body and said porous body enclosing a supply chamber, the pores of said porous body forming the only passages from within said chamber onto the outer surface of said porous body, a supply substance provided within said supply chamber and adapted to work as the active material for said cathodes, said porous body being formed by a metallic material having a content of at least one of the platinum metals and adapted to form an alloy with at least a substantial portion of the metal yielded by said supply substance along their contacting surfaces, said supply substance containing at least one of the alkaline metals and alkaline earth metals in form of an alloy and adapted to yield, at least in the activated condition of the cathode such a metal in its metallic state through the passages of said porous body for continuously rendering active said working surface.

2. A cathode-ray tube for use in television receivers, having an electron gun, accelerating electrons, detlecting means, and a uorescent screen, the cathode of the electron gun being a supply cathode having a working surface and comprising a container body, a sintered porous body for serving as `a closing member of said container body, said container body and said porous body enclosing a supply chamber, the pores of said porous body forming the only passages from within said supply chamber onto the outer surface of said porous body, a supply substance provided Within said supply chamber `and adapted to Work as the active material for said cathode, said porous body being formed by a metallic material having a content of at least one of the groups of the platinum metals and adapted to form an alloy with at least the substantial portion of the metal yielded by said supply substance along their contacting surfaces, said supply substance containing at least one of the alkaline metals and alkaline earth metals in form of an alloy and adapted to yield, at least in the activated condition of the cathode, such a metal in its metallic state through the passages in said porous body for continuously rendering `active said working surface, the velocity of vaporization of said alloy being determined by the ratio of the active and inactive components of said alloy.

3. A cathode-ray tube, as claimed in claim 1, for use in television receivers, said cathode comprising a container body, a sintered porous body for serving as a closing member of said container body, said container body and said porous body enclosing a supply chamber, the pores of said porous body forming the only passages from within said chamber onto the outer surface of said porous body, a supply substance provided within said supply chamber and adapted to work as the active material for said cathode, said supply substance consisting of an alloy made, on the one hand, of at least one of the metals barium, strontium, calcium and, on the other hand, of at least one metal of the group III of the Periodic System, the velocity of vaporization of said alloy being determined by the ratio of the active and inactive components of said alloy.

4. A cathode for cathode-ray tubes, as claimed in claim l, for use in television receivers, said cathode comprising a container body, a sintered porous body for serving as ya closing member of said container body, said container body and said porous body enclosing a supply chamber, the pores of said porous body forming the only passages from within said chamber onto the outer surface of said porous body, a supply substance provided Within said supply chamber and adapted to work as the active material for said cathode, said supply substance consisting of an alloy made, on the one hand, of barium and strontium and, on the other hand, of at least one material of the group III of the Periodic System, the velocity of vaporization of said alloy being determined by the ratio of the active and inactive components of said alloy.

5. A cathode for cathode-ray tubes, as claimed in claim l, for use in television receivers, said cathode comprising a container body, a sintered porous body for serving as a closing member of said container body, said container body and said porous body enclosing a supply chamber, the pores of said porous body forming the only passages from Within said chamber onto the outer surface of said porous body, a supply substance provided within said supply chamber and adapted to work as the active material for said cathode, said supply substance consisting of an alloy made, on the one hand, of barium and calcium and, on the other hand, of at least one metal of the group III of the Periodic System, the velocity of vaporization being determined by the ratio of the active and inactive components of said alloy.

6. A cathode for `cathode-ray tubes, as claimed in claim 1, for use in television receivers, said cathode comprising a container body, a sintered porous body for serving as a closing member of said container body, said container body and said porous body enclosing a supply chamber, the pores of said porous body forming the only passages from Within said chamber onto the outer surface of said porous body, a supply substance provided within said supply chamber and adapted to Work as the active material for said cathode, said supply substance consisting of a barium-aluminum alloy, the velocity of vaporization being determined by the ratio of the active and inactive components of said alloy.

7. A cathode according to claim 6, comprising a supply substance as activator containing at least 20% barium, the velocity of vaporization being determined by the ratio of the active and inactive components of said alloy.

8. A cathode for cathode-ray tubes, as claimed in claim 1, for use in television receivers, said cathode comprising a container body, a sintered porous body for serving as a closing member of said container body, said container body and said porous body enclosing a supply chamber, the pores of said porous body forming the only passages from within said chamber onto the outer surface of said porous body, a supply substance provided Within said supply chamber and adapted to Work as the active material for said cathode, said supply substance consisting of an alloy containing about 50% barium and about 50% aluminum, the velocity of vaporization being determined by the ratio of the active and inactive components of said alloy.

9. A cathode for cathode-ray tubes, as claimed in claim l, for use in television receivers, said cathode comprising a container body, a sintered porous body for serving as a closing member of lsaid container body, said container body and said porous body enclosing a supply chamber,

the pores of said porous body forming the only passages from within said chamber onto the outer surfaceof said porous body, a supply substance provided within` said :supply chamber and adapted to work as the active material for said cathode, said supply substance consisting o-f an alloy containing about 40% barium, about 10% calcium and about 50% aluminum, the velocity of vaporization being determined by the ratio of the active and inactive components of said alloy.

10. A cathode for cathode-ray tubes, as claimed in claim 1, for use in television receivers, said cathode comprising a container body, a sintered porous body for serving as a closing member of said container body, said container body and said porous body enclosing a supply chamber, the pores of said porous body forming the only passages from within said chamber onto the outer surface of said porous body, a supply substance provided within said supply chamber and adapted to Work as the active material for said cathode, said supply substance consisting of an alloy containing about 40% barium, 20% aluminum and 40% nickel, the velocity of vaporization being determined by the ratio of the active and inactive components of said alloy.

References Cited in the le of this patent UNITED STATES PATENTS Brown July 28, 1953 

